Multiple choice technology programming languages

class C { int a, b, c; public void setA(int i) {a = i; assert validateC() : c;} public void setB(int i) {b = i; assert validateC() : c;} private boolean validateC() { return c > a + 2 * b; } public int m1(int i) { c = a + b + i; assert validateC() : c; return c; } public C(int i) { c = i; assert validateC() : c; } public static void main(String[] args) { C c = new C(251); c.setA(50); c.setB(100); }} Which statements are true?

  1. If assertions are not enabled at run time it prints an error message.

  2. If assertions are not enabled at run time it prints nothing.

  3. With assertions enabled it prints an error message.

  4. With assertions enabled it prints nothing.

  5. The assert statement is being used to check a class invariant--something that must be true about each instance of the class

  6. The assert statements are being used to check a precondition--something that must be true when the method is invoked.
Reveal answer Fill a bubble to check yourself
B,D,E Correct answer
Explanation

If assertions are disabled, assert statements are ignored, printing nothing. With assertions enabled, the constructor and setter calls succeed because the invariant c > a + 2 * b holds (e.g., 251 > 50 + 200 is true), so nothing is printed. The assertions check a class invariant.

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